The Army trusts soldiers with weapons and ammunition after advanced training. Does it mean I want Pvt. Snuffy as the sole demonstrator in front of an audience with no supervision?

Nope.

I've had Privates out on observation posts by themselves. Doesn't mean I'm going to use them as subject matter experts to give a class on manning an observation post.

It was a relatively green rookie given a job I've always seen done by far more experienced officers. It's the leadership's fault for putting him in a position he isn't mature or experienced enough to handle, and his fault for letting them egg him into tasing them (which, according to other news articles, wasn't a full taser shot)